Muffler for an exhaust system

Abstract

A muffler (1) for an exhaust system of an internal combustion engine has a housing (2) with an expansion chamber (6). An inlet pipe (7) extends into the housing (2) and has an end section (8) with an outlet opening (9) to the expansion chamber (6). A main outlet pipe (10) has an initial section (11) protruding into the end section (8) of the inlet pipe (7). A secondary outlet pipe (15) has an inlet opening (16) in the expansion chamber (6). A gap (14) in an overlapping area (13) between the end section (8) and the initial section (11) forms a bypass in the end section (8) of the inlet pipe (7), which bypasses the initial section (11) of the main outlet pipe (10). Through the bypass gap (14), exhaust gas flows from the inlet pipe (7) into the expansion chamber (6) and out the secondary outlet pipe (15).

Claims

1. A muffler for an exhaust system of an internal combustion engine, the muffler comprising: a housing, in which an expansion chamber is formed; an inlet pipe extending into the housing and introducing exhaust gas into the housing, the inlet pipe having an end section with an outlet opening in the expansion chamber; a main outlet pipe extending into the housing and removing exhaust gas from the housing, the main outlet pipe having an initial section which protrudes into the end section of the inlet pipe; a gap formed in an overlapping area between the end section of the inlet pipe and the initial section of the main outlet pipe and which forms a bypass, through which exhaust gas can flow from the inlet pipe into the expansion chamber, which bypass bypasses the initial section of the main outlet pipe in the end section of the inlet pipe; and a secondary outlet pipe having an inlet opening in the expansion chamber and removing exhaust gas from the housing.

2. A muffler in accordance with claim 1, wherein: the end section of the inlet pipe and the initial section of the main outlet pipe each have a straight configuration; and an axial length of the overlapping area is at least twice a diameter of the end section of the inlet pipe.

3. A muffler in accordance with claim 1, wherein flow cross sections or flow resistances or both flow cross sections and flow resistances of the main outlet pipe, the secondary outlet pipe and the gap are coordinated with one another such that 40% to 60% of the exhaust gas stream fed via the inlet pipe is removed through the main outlet pipe at partial load of the internal combustion engine.

4. A muffler in accordance with claim 1, wherein a flow cross section of the gap in an overlapping area is, on average, about equal to a flow cross section of the main outlet pipe.

5. A muffler in accordance with claim 1, wherein the housing has a cylindrical configuration and has a jacket as well as two end panels; the inlet pipe passes through the jacket; the main outlet pipe passes through the one end panel; and the secondary outlet pipe passes through the other end panel.

6. A muffler in accordance with claim 1, wherein the inlet pipe is unperforated; or the main outlet pipe is unperforated or the secondary outlet pipe unperforated; or any combination of the inlet pipe is unperforated and the main outlet pipe is unperforated and the secondary outlet pipe unperforated.

7. A muffler in accordance with claim 2, wherein the inlet pipe has a perforation in the overlapping area.

8. A muffler in accordance with claim 1, wherein: at least one additional chamber is formed in the housing; and the inlet pipe has perforations or the secondary outlet pipe has perforations or both the inlet pipe has perforations and the secondary outlet pipe has perforations, at least in the additional chamber.

9. A muffler in accordance with claim 1, further comprising: a sound-absorbing material; a perforated first partition in the housing; and an unperforated second partition in the housing, wherein: a first additional chamber is formed in the housing that axially adjoins the expansion chamber via the first partition; a second additional chamber is formed in the housing that axially adjoins the first additional chamber via the second partition, on a side facing away from the expansion chamber; the first additional chamber is configured as an absorption chamber filled with the sound-absorbing material, and is acoustically coupled with the expansion chamber via the perforated first partition; and the second additional chamber is configured as a resonator chamber, which is separated from the first additional chamber via the unperforated second partition and is acoustically connected to the secondary outlet pipe or to the expansion chamber via a resonator tube.

10. A muffler in accordance with claim 1, wherein the main outlet pipe is radially supported in the overlapping area at the inlet pipe.

11. A muffler in accordance with claim 10, further comprising a plurality of webs, wherein the main outlet pipe is supported at the inlet pipe via the plurality of webs, which are arranged distributed in the circumferential direction of the main outlet pipe and bridge over the gap.

12. A muffler in accordance with claim 10, further comprising at least one perforated ring, wherein the main outlet pipe is supported at the inlet pipe via the at least one perforated ring, which extends in a circumferential direction of the main outlet pipe and fills the gap.

13. A muffler in accordance with claim 1, further comprising a perforated intermediate panel wherein the main outlet pipe is supported at the perforated intermediate panel, which is arranged in the expansion chamber and is supported at the housing.

14. A muffler in accordance with claim 1, further comprising a control device controlling an opening of the main outlet pipe at least at full load of the internal combustion engine and a closing the main outlet pipe at least at a low partial load, whereby the main outlet pipe is flow controlled.

15. An exhaust system for an internal combustion engine, the exhaust system comprising: an exhaust line, which leads from at least one branch of an exhaust manifold to at least one tail pipe; and a muffler connected to the exhaust line, the muffler comprising: a housing, in which an expansion chamber is formed; an inlet pipe extending into the housing and introducing exhaust gas from the exhaust line into the housing, the inlet pipe having an end section with an outlet opening in the expansion chamber; a main outlet pipe extending into the housing and removing exhaust gas from the housing, the main outlet pipe having an initial section which protrudes into the end section of the inlet pipe; a gap formed in an overlapping area between the end section of the inlet pipe and the initial section of the main outlet pipe and which forms a bypass, through which exhaust gas can flow from the inlet pipe into the expansion chamber, which bypass bypasses the initial section of the main outlet pipe in the end section of the inlet pipe; and a secondary outlet pipe having an inlet opening in the expansion chamber and removing exhaust gas from the housing.

16. An exhaust system in accordance with claim 15, wherein: the end section of the inlet pipe and the initial section of the main outlet pipe each have a straight configuration; an axial length of the overlapping area is at least twice a diameter of the end section of the inlet pipe; and a flow cross section of the gap in an overlapping area is, on average, about equal to a flow cross section of the main outlet pipe.

17. An exhaust system in accordance with claim 15, wherein flow cross sections or flow resistances or both flow cross sections and flow resistances of the main outlet pipe, the secondary outlet pipe and the gap are coordinated with one another such that 40% to 60% of the exhaust gas stream fed via the inlet pipe is removed through the main outlet pipe at partial load of the internal combustion engine.

18. An exhaust system in accordance with claim 15, wherein: at least one additional chamber is formed in the housing; and the inlet pipe has perforations or the secondary outlet pipe has perforations or both the inlet pipe has perforations and the secondary outlet pipe has perforations, at least in the additional chamber.

19. An exhaust system in accordance with claim 15, further comprising: a sound-absorbing material; a perforated first partition in the housing; and an unperforated second partition in the housing, wherein: a first additional chamber is formed in the housing, that axially adjoins the expansion chamber via the first partition; a second additional chamber is formed in the housing, that axially adjoins the first additional chamber via the second partition, on a side facing away from the expansion chamber; the first additional chamber is configured as an absorption chamber filled with the sound-absorbing material, and is acoustically coupled with the expansion chamber via the perforated first partition; and the second additional chamber is configured as a resonator chamber, which is separated from the first additional chamber via the unperforated second partition and is acoustically connected to the secondary outlet pipe or to the expansion chamber via a resonator tube.

20. An exhaust system in accordance with claim 15, further comprising a control device controlling an opening of the main outlet pipe at least at full load of the internal combustion engine and a closing the main outlet pipe at least at a low partial load, whereby the main outlet pipe is flow controlled.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the drawing:

(2) FIG. 1 is a highly simplified, circuit-diagram-like general view of a muffler.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) Referring to the drawings, corresponding to FIG. 1, a muffler 1, which is intended for an exhaust system of an internal combustion engine, comprises a housing 2, which preferably has a cylindrical configuration and correspondingly has a cylindrical jacket 3 and, at its axial ends, an end panel each, namely, a first end panel 4 and a second end panel 5. The exhaust system and the internal combustion engine are advantageously arranged in a road vehicle. The vehicle is preferably an automobile, especially a sports car.

(4) An expansion chamber 6 is formed in the housing 2. This expansion chamber is characterized by a free space, into which exhaust gas and airborne sound being carried by same can expand. Sound-absorbing material may optionally be arranged in the expansion chamber 6 outside this free space, e.g., along limiting walls.

(5) The muffler 1 is equipped with an inlet pipe 7, which has in the housing 2 an end section 8, with which the inlet pipe 7 ends in the expansion chamber 6. The end section 8 has an outlet opening 9 for this in the expansion chamber 6. Further, the muffler 1 is equipped with a main outlet pipe 10, which has an initial section 11 in the housing 2. This initial section 11 is inserted into the end section 8 of the inlet pipe 7 and ends in the interior of the inlet pipe 7. The initial section 11 is correspondingly shown in FIG. 1 with broken line only. The initial section 11 has an inlet opening 12 within the inlet pipe 7. Since the initial section 11 of the main outlet pipe 10 protrudes into the end section 8 of the inlet pipe 7, an overlapping area 13, which is indicated by a curly bracket in FIG. 1, is formed between the end section 8 and the initial section 11. A gap 14 is formed in this overlapping area 13 radially between the end section 8 and the initial section 11. This gap 14 forms, in turn, a bypass, which bypasses the initial section 11 within the end section 8. Exhaust gas can thus flow through the gap 14 from the inlet pipe 7 past the initial section 11 on the outside into the expansion chamber 6. Finally, the muffler 1 has, in addition, a secondary connection pipe 15, which has an inlet opening 16 in the expansion chamber 6.

(6) The end section 8 of the inlet pipe 7 and the initial section 11 of the main outlet pipe 10 advantageously extend as straight sections, so that the overlapping area 13 is straight as well. The initial section 11 axially protrudes into the end section 8 to the extent that the overlapping area 13 has an axial length 17 that is about four times the diameter 18 of the inlet pipe 7 in the end section 8 in the example being shown. A resonance effect, with which a certain frequency of the sound being transported in the exhaust gas can be muffled, can be optimized in the main outlet pipe 10 by the insertion depth or by the length 17 of the overlapping area 13.

(7) The flow cross sections and flow resistances of the main outlet line 10, of the secondary outlet line 15 and of the gap 14 are advantageously coordinated with one another such that a predefined split of an exhaust gas stream 19 being fed via the inlet pipe 7 into a primary partial stream 20 removed through the main outlet pipe 10 and a secondary partial stream 21 being removed through the secondary outlet pipe 15 becomes established at least at partial load and/or full load of the internal combustion engine. The global flow 19 being fed, namely, the main partial stream 20 and the secondary partial stream 21, are indicated by arrows in FIG. 1. A split of the global stream 19 to the primary partial stream 20 and the secondary partial stream 21 that is in a range of 40:60 to 60:40 is preferably set. A split of about 50:50 is especially advantageous.

(8) To achieve a splitting of the global stream 19 into the primary partial stream 20 and the secondary partial stream 21, provisions may be made for selecting in the overlapping area 13 the flow cross section of the gap 14 to be, on average, about equal to the flow cross section of the main outlet pipe 10 in the initial section 11. The flow cross sections of the gap 14 and of the initial section 11 are accordingly always about half the flow cross section of the inlet pipe 7 directly upstream of the inlet opening 12 of the main outlet pipe 10.

(9) Even though a concentric arrangement of the initial section 11 and end section 8, which leads to a gap 14 extending fully in a ring-shaped pattern around the initial section 11, is shown in FIG. 1, any desired eccentric arrangement may, in principle, be selected. It is also conceivable, in particular, that the initial section 11 linearly touches the end section 8. It is likewise conceivable that the end section 8 and the initial section 11 have a common wall section, which is limited in the circumferential direction of the overlapping area 13. The gap 14 may also have different geometries depending on the cross-sectional geometry of the initial section 11 and end section 8 in the overlapping area 13. It may be, e.g., ring-shaped or C-shaped in case of round pipe cross sections and U-shaped or I-shaped in case of angular, preferably rectangular, pipe cross sections.

(10) The inlet pipe 7 is passed through the jacket 3 in the preferred embodiment being shown here with cylindrical housing 2, while the outlet pipes 10 and 15 are passed through the end panels 4, 5. Specifically, the main outlet pipe 10 is passed through the first end panel 4, while the secondary outlet pipe 15 is passed through the second end panel 5. Provisions may also be made, as an alternative, for both outlet pipes 10, 15 to be passed through the same end panel 4 or 5.

(11) Furthermore, two additional chambers, namely, a first additional chamber 22 and a second additional chamber 23, are formed in the housing 2 in the embodiment being shown here. The first additional chamber 22 axially adjoins the expansion chamber 6. The second additional chamber 23 axially adjoins the first additional chamber 22 on a side facing away from the expansion chamber 6. The axial direction is defined here by a central longitudinal axis 24 of the cylindrical housing 2. The first additional chamber 22 is separated from the expansion chamber 6 by means of a first partition 25 and is separated from the second additional chamber 23 by means of a second partition 26. Preferred is an embodiment in which the first additional chamber 22 is configured as an absorption chamber and is filled with a sound-absorbing material 27. The first additional chamber 22 is preferably filled completely with a sound-absorbing material 27. Further, the first partition 25 is preferably perforated. The first additional chamber 22 is thus acoustically connected to the expansion chamber 6. The inlet pipe 7 and the secondary outlet pipe 15 pass through the first partition 25 here. The second partition 26 is preferably configured as an unperforated partition. The second additional chamber 23 may preferably be configured as an expansion chamber or as an absorption chamber or as a resonance chamber. Furthermore, an embodiment is preferred, in which the inlet pipe 7 and the main outlet pipe 10 are unperforated. Contrary to this, the secondary outlet pipe 15 in the second additional chamber 23 may be provided with a perforation 28, whereby the second additional chamber 23 is acoustically coupled with the secondary outlet pipe 15. The secondary outlet pipe 15 may be unperforated in the first additional chamber 22 or have an additional perforation, not shown here. In connection with the perforation 28, the second additional chamber 23 forms an additional expansion chamber.

(12) Instead of the perforation 28 shown, a resonator tube 29 indicated by a broken line, which forms a Helmholtz resonator in connection with the free volume of the second additional chamber 23, may also be provided at the secondary outlet pipe 15.

(13) Provisions may preferably also be made for using a resonator tube 32 for acoustically connecting the expansion chamber 6 to the second additional chamber 23 in order to form such a Helmholtz resonator. The second additional chamber 23 is a resonator chamber in this case as well. The resonator tube 32 passes through the perforated first partition 25 and the unperforated second partition 26 as well as the first additional chamber 22, which acts as an absorption chamber in this case. Further, the secondary outlet pipe 15 and the inlet pipe 7 are unperforated in this case at least in the second additional chamber 23.

(14) It is likewise conceivable, as an alternative, to provide, in addition to the perforation 28, a connection pipe 30, which is likewise indicated by an interrupted line only in FIG. 1. This connection pipe 30 will then interact with the free volume of the first additional chamber 22 as a Helmholtz resonator. It may be advantageous in this case to configure the second additional chamber 23, which is acoustically connected to the secondary outlet line 15 via the perforation 28, as an absorption chamber, which is then filled with sound-absorbing material 27.

(15) In addition, FIG. 1 indicates a control device 31, by means of which the ability of exhaust gas to flow through the main outlet pipe 10 can be controlled. In particular, the splitting of the global stream 19 into the primary partial stream 20 and the secondary partial stream 21 can be varied hereby. For example, the control device 31 can open the main outlet pipe 10 at full load of the internal combustion engine, so that a comparatively large primary partial stream 20 will develop. In a lower partial load range, the control device 31 may, by contrast, bring about a blocking of the main outlet pipe 10, so that a comparatively large secondary partial stream 21, which corresponds to the global stream 19 in the extreme case, will then develop. This optional control device 31 is arranged outside the housing 2 in the example being shown. In another embodiment, the control device 31 may also be arranged on the housing 2 or in the housing 2.

(16) Provisions are made, in addition, according to FIG. 1 for the main outlet pipe 10 to be radially supported in the overlapping area 13 at the inlet pipe 7. This is accomplished in the example being shown in the area of the inlet opening 12 of the main outlet pipe 10 by means of a plurality of webs 33, which support the main outlet pipe 10 at the inlet pipe 7 and which are arranged distributed in the circumferential direction of the main outlet pipe 10 and at spaced locations from one another and bridge over the gap 14. In addition, a perforated ring 34 is provided in the example in the area of the outlet opening 9 of the inlet pipe 7, wherein the main outlet pipe 10 is supported via said ring at the inlet pipe 7 and said ring extends in the circumferential direction of the main outlet pipe 10 and fills the gap 14. Finally, provisions are made here, in addition or alternatively, for the main outlet pipe 10 to be supported at a perforated intermediate panel 35, which is arranged in the expansion chamber 6 and is supported at the housing 2.

(17) Thus, a pipe-in-pipe arrangement of the inlet pipe 7 and main outlet pipe 10, which arrangement makes possible a quasi uninterrupted flow through the housing 2 if the main outlet pipe 10 is opened, is thus created in the overlapping area 13. A main exhaust gas path is thus created by this pipe-in-pipe arrangement through the housing 2. If, in addition, the inlet pipe 7 and the main outlet pipe 10 are unperforated and the end section 8 and, in particular, the initial section 11 are also unperforated in the overlapping area 13, there is only a very weak acoustic coupling via this quasi contiguous pipe with the acoustic muffling devices of the muffler 1. In particular, only a comparatively small volume of the muffler 1 is coupled to this main path. These acoustic muffling devices are, for example, as was explained above, the expansion chamber 6, the first additional chamber 22 and the second additional chamber 23, which may optionally act as an expansion chamber, as an absorption chamber and as a resonance chamber of a Helmholtz resonator. With the main outlet pipe 10 opened, the airborne sound being carried in the global stream 19 can leave the muffler 1 through the main outlet pipe 10 largely unmuffled along the main exhaust gas path, as a result of which the driver of the vehicle receives the desired feedback. If, by contrast, the main outlet pipe 10 is closed, the airborne sound being carried in the global stream 19 is forced to follow the secondary exhaust gas path passed through the secondary outlet pipe 15, while all muffling devices provided are active and correspondingly bring about an efficient muffling of the airborne sound being carried. Further, the coupling of the main outlet pipe 10 acting as a resonance tube can be optimized by the pipe-in-pipe arrangement.

(18) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.